Smokeless explosive powder and process of making same



Patented May 10, 1927.

. UNITED STATES;

, rRANcIs I. nu-ronr-AND ERNEsr Du rou'r, or wrmume'rou, DELAWARE, AssIeuoRs,

.IBY mEsuE ASSIGNMENTS, r 1:. s. F. POWDER COMPANY, or wrnmme'ron, DELA- W RE, A coRroRArIoN or DELAWARE.

smox'E Ess ExrLosIvE rowDER AND rRocEss or MAKING sAME'.

No Drawing. ,Original application its January 24, 1919, Serial No. eraser. Divided and this application filed April 24, 1920, Serial No. 376,267. Renewed January 24, 1921, Serial No. 439,689. This application filed. August 8, 1921, Serial'No. 490,728.

This invention relates, to flashless powders and processes of producing: the same, and it comprises a powder having an accelerat ng rate of combustion of such a'nature. as to 5 deliver muzzle gases not igniting in contact with air, such powder comprising a cellular body or matrix of colloided nitrocellulose containing includedsolid particles adapted to produce corresponding open cells or cavities duringthe combustion of the 'powder;

and it further comprises a method of producing such a powder wherein nitrocellulose is intimately admixed with solid particles ofblack powder, or of.an ox en-evolving,

'1 combustion quickening materla, such as a.

mixture of potassium nitrate and barium nitrate, and colloided to producea hone comb structure with the admixed solids in the cells, etc., all asmore iully hereinafter set forth and as claimed.

The obl'ect of our invention isto produce a smoke ess explosive ordnance powder which, when used as a pro llant charge in a gun, will approximately eliminate, or at least very 'materially reduce, the muzzle flash; that is, light-emitting combustion or explosion beyond the muzzle. To accomplish this it is necessary'that the powder should ,be v substantially. consumed and combustion acno tions over. before the gas'eousmass emerges from the muzzle of the gun. It is not merely sufiicient that the composition and structure of the powder should be such as to-p'romote rapid accelerative burning, but it is also es- :as sential that this rapid burning should be cflt'ected without substantial, increase of chamber pressure in order thereby to avoid erosion of the gun barrel.

. It the usual practice toefiect the burn- 40 ing of ordnance powder in a progressive way by forming perforations through the Zmass of a powder-grain, so that the grains, which are rather large sized units requiring appreciable .time for complete combustion, will burn from the inside as well as from the outside, thus exposing. to the flame, as the burning proceeds, a progressively increasing superficial area. There is a progressive acceleration of combustion.

The manufacture of smokeless'explosives from nitrocellulose or pyroxylin is now'anold art and such powders'are usually colloided; a term used in .the art to' designate a treatment with solvents (usually acetone or ether-alcohol) to remove structure and convert the pyroxylin into an amorphous integral body. The solvents may be used in quantity suflicient to make a solution or in amoungmerely suflicient to plasticize; the

final result being the same. These colloided smokeless powders arerelatively slow burning and in; order to accelerate combustion and'p'roduce a difierent pressure curve in the gun, it is usual to use them as perforated grains. Combustion on the walls widens these perforations, ofiering a constantly increasing burning area. Conditions are ordi narily so adjusted as to cause a maximum rate of combustion just before the rojectile leaves the muzzle. In the actions in a gun, the work done on the projectile and gas expansion are heat-absorbing, while combustion is' heat-developin these balancing against each other. y postponing the maximum heat evolution in the way in which it is done-in these perforated'powders, the

1 gases leave the muzzle very hot. .And-as -pyroxylm contains an excess of carbon, the muzzle gases are combustlble, causing a secondary combustion or explosion with the aid of air, this giving the flash.

We have discovered that the rate of progression acceleration-of the burnin in this type -of powder may be substantially increased, without increase of chamber pres sure, by distributing in a colloided mass of nitrocellulose powder a flame propagating agent which will carryitheflame from the exposed surfaces. throu h a multitude of nmate developed'channe s, into the interior of the powder grains, thereby bringing all the colloided nitrocellulose much more speedily into progressive contact with the fire and-effecting an earlier complete coi1 sumption of the, powder than is the case where reliance is had solely upon relatively large and coarse mechanical perforations.

In the present invention a different type of burning is superimposed on that resulting 1 from these perforations. It has been assumed. that the flash produced at the muzzle of a i the fapti ;.that prope substantially entire :jlight n -isdue to t pow erscomposed nitrocellulose have nitrate and potassium nitrate.

an actual deficiency of oxygen below that which would be necessary to burn all of the carbon, and that minute particles of carbon, intensely heated, actually escape from the muzzle of a gun and combine with the oxygen of; the atmosphere in precisely the same way as do the particles of carbon in-an ordinary jet of illuminating gas. In other words, there is a secondary combustion or explosion beyond the muzzle; this giving the flash. While this may he a correct explanation of the phenomenon, we have found by prolonged experiment that in suppressing flash by the use of our agents in our way, it is not essential that the ingredients added shall actually contain an excess of oxygen; that is, it isnot necessary to try to burn the excess of carbon in the gun. In fact, we have used with equal success one flame propagating agent having an excess of oxygen and another inv which there is no oxygen available for the nitrocellulose, with an equal degree of success.

In the present invention, we superimpose upon the old type of acceleration by the aid of perforations, another type resulting from progressively developing cavities in the grain; a sort of pitting action. In so doing,

we are enabled to obtain a new type of combustion. And -we have found that by proper regulation "of the details of manufacture, we can produce a colloided pyroxylin powder which will develop satisfactory pressure curves in the gun, while at the same time permitting the gases to leave the muzzle at a temperature at which, or in a condition in which, they will not ignite with theair. In other words, we do away with the secondary combustion or explosion which occurs beyond the muzzle ,with the ordinary types of perforated, colloided nitrocellulose. In our new powder-we usually employ the ordinary perforations and in addition give the 'colloided pyroxylin a cellular or honeycomb structure: the cells being filled with solids adapted to cause quick local action and development of free cell walls adapted for free combustion.

If a particle or grain of a quicker-burning explosive, such as black powder, be contained within a body of 'colloided nitro-' cellulose, when ignition reaches this grain, it disappears, leaving a pit or cavity in the nitrocellulose and then combustion follows along the cavity walls. The effect is as it a new perforation had just been made at this point. The same result may be obtained by using crystals .or'particles of oxygen-evolving substances, such as a mixture of barium loided nitrocellulose containing a particle of such a substance, when ignition reaches the article, there IS a local evolution of oxygen ,which quickens combustion of the nitroc'ellulose lying next the particle. opening up In acol-.-

a space along the interface and giving the result'of a newly developed pit or cavity.

While the way in which the black powder I and the oxidant actin' developing pits or cavities is different in detail, the result is the same; progressive opcning-of-pits or cavities and, avoidance of flash. VVi-th oxygen-evolving substances, if the amount employed be suflicient, the excess of carbon in the pyroxylin is consumed, giving muzzle gases which will not burn. In certain co-pendmg applications, we

have described and claimed various powders and processes of making the same embody-v ing the stated principles. In the applica-' tion filed June 12, 1918, under-SerialNo. 239,531, we described andclai'med the manufacture of a powder wherein pyroxy lin was first mixing nitrocellulose and either black powder or a mixture of barium and potassium nitrate aiid afterwards .colloiding, but. restricted the claims to the uscof such nitrates. In another application, originally filed February 23, 1921, as Serial ,No. 447.- 229, we describe and claim another embodispecific flame propagating agent is a bichromate. or a mixture o'f.-a bichromate and carbon. In the present application,-we describe and claim, in the specific claims, the use of black powder as a flame propagating agent. a -It is not sufficient that the added flame propagating agent shall merely'be. efi'ective to expedite the consumption of the nitrocellulose, but it must be such an agent as will do this without,substantially increasing the chamber pressure, without 'scriously fouling the gun and without producing an excess of smoke. This not merely materially. narbe otherwise available, but after the I-proper substances have been asccrtainedyeby'experiment, the further problem ariseslof adding them in proper proportions to the nitrocellulose. acquired, the addition of the flame propagating agent to the nitrocellulose must precede any substantial colloiding of the nitro- -ccllulose. T

The characteristics ot a fire propagating agent such as black powdei and of a'firepropagating agent such 'as a mixture of ment of the present invention wherein the rows the range of substances which would Finally. after this information is. p

barium and potassium nitrates are, of course, quite dissimilar, the most notable difference being that the latter has an excess of oxygen, which it evolves when heated, while the former is a complete explosive and has no available oxygen.

\Vhere a mixture of the two salts above named is used, we prefer to use about two parts of the barium salt to one part of the potassium salt, although these proportions may be varied. The total of the two ingredients should form about 8 to 12 per cent of the entire explosive. In no use should it exceed 20 per cent, whilewe distinctly prefer not to exceed 15 per cent. On the other hand, the proportion maybe'as low as 4 per cent and still very materiallyreduce the flash, although we prefer a minimum of about 7 or 8 per cent.- The objection to using a large proportion of this fire propagatlng agent is that it results in objectionably fouling the gun, and moreover; a relatively large proportion produces no useful effect in the elimination of the flash, thi'i being, for all practical purposes, attained by a relatively small prpportion.

Where black powder is used as the flame propagating agent, we may use about the same proportion as above specified for the nitrates. A needlessly large proportion of black powder will produce an objectionable amount of smoke and should be carefully avoided. We prefer, therefore, to we as small a percentage of black powder as is possible, consistent with securing the desired results. As low as two per cent of black powder gives substantially fiilSlllBf-S results and the black powder content may even be reduced to one-half of one per cent and still very materially reduce the flash.

Whether the flame pro agating agent be one or the other of the above materials, or some equivalent substance, or combination of substances, the process of adding the agent to the nitrocellulose is of great importance. Unless the a cut be so added as to effect a very thorough and intimateassooiation of the particles, the finished powder will give non-uniform and uncertain results as a commercial product, in which uniformity and certainty of action are essential.

In carrying out our process it is necessary, in order to secure certain and uniform results, to thoroughly incorporate the flame propagating agent with the nitrocellulose before colloiding. We proceed by taking soluble nitrocellulose and add thereto the specified proportion of the 'flame producing agent, ,wet it with aboutthirty per cent of a suitable blending liquid, such as water or gasoline, and incorporate the same in a standard black powder wheel -.mill for about an hour or an hour and a quarter. The liquid added should be one which does not chemically combine with the explosive ingredients, or does not combine with them except to form a solution from which the solvent may be expelled by drying or by displacement otherwise. We prefer to use gasoline. \Vithout the thorough moistening ot' the powder, the mixing operation, in any mill of the kind specified, would be attended with serious danger.

After the ingredients are thus incorporated, the added liquid, it, is expelled by drying orotherwiseand then the colloiding agents, ether and alcohol, are added, and the entire mixture is thoroughly colloided in a kneading machine for about an hour. After the powder has been formed into grains of the usual type employed in ordnance, a considerable proportion of alcohol and ether is distilled oil", a certain proportion remaining in the finished product.

The removal of the alcohol and ether rhou d not be efi'ected in any way whichwill came removal of the tire carrying agent, as that would produce a certain undesirable porosity in 'the finished powder, whereas thoroughly porosity, or porosity alone, is not the result desired, but rat-her a proper dissemination of the fire propagatingagent through colloided nitrocellulose. The thorough incorporation of the ingredientsis of the utmost importance, and it seems to be practically e'sential to first thoroughly incorporate the lire propagating agent with the nitrocellulose and afterward colloid; in other words, to rather closely adhere to the procedure above described.

The resultant powder is, to all intents and or most of III purposes, flashless, there'is no SElltltli foulmg of the gun, and the smoke produced is rtgllimite'd in volume as-to be-unobjectiona c.

If the colloiding agent be added. at the beginning of the mixing operation, substant al incorporation of the nitrocellulose and the fire propagating agent will neverthelcss occur before the colloiding action, and a flashless powder will be ultimately produced, but it is distinctly advantageous to add the colloiding agent after the operation of mixing the soluble nitrm'ellulose and tire propagating agent has been completed and after the expulsion of the liquid.

INT

It should be clearly understood. however,

that the colloiding of the nitrocellulose prior to the addition of the fire propagating agent would be, in substance, theaddition of such agent to smokeless powder, and would be ineffective in accon'iplishing the purposes of our invention. Moreover, black powder, and various salts, have been added to certain' so-called smokeless or sen'ii smokelcss powders in other proportions and in "other ways for-other purposes.

In specifying a flame propagatingagent we do not use the words to mean substances when added to ingredients other than col loided nitrocellulose, ,render them combustible or increase their rate of hearing;

. but it is intended to be confined to substances which, contained in colloided nitrocellulose, will, by themselves, or in conyunction with such colloided nitrocellulose, in-:

crease the rate of burning of the explosives,

as herein deSCXlbQtl, substantially beyond the rate of burning of colloided nitrocellulose alone.

We intend herein to claim the use of a flame propagating agent generically, and the use of black powder specifically; other pending applications hereinbetore recited being specific to certain other flameipropagating agents.

Having now fully described our invention,

ters Patent is.

i 1. The process of makin flashless smokeless propellant powder with a progressirely increasing rate of, burning whichcomprises addin to and thoroughly incorporatmg with solu le nitrocellulose a flame propagating agent, and afterward completely 'colloiding with ether and alcohol and retaining the flame propagating agent in the finished. explosive. p 2. The process of making flashless smokeless propellant powder with a progressively increasing rate of burnin comprises adding to soluble nitroce lulose a flame propagating agent, moistening with a liquid adapted to be afterward expelled, thoroughly incorporating, expelling the added liquid, and. colloiding with ether and alcohol. 4

3. The process of making flashless smokeless propellant powder with a progressively increasing rate of burnin which comprises-adding to and thorough y, ineor-' porating with soluble nitrocellulose between from one-half of one per cent to twenty per cent of a flame propagating agent and completely colloiding with ether and alcohol.-

4. The process of making flashless smokeless propellant powder which comprises adding to and thoroughly incorporating with soluble nitrocellulose a. relatively small proportion of black powder and after-- ward colloiding with ether and alcohol.

The process of making fiashless smokeless propellant powder which comprises adding to soluble nitrocellulose a small proportion of black powder, intimately incorporating said nitrocellulose and 'said black powder, and then colloiding the nitrocellulose with a suitable solvent.

' (3. The process of making plosive powder with a progressively increas- ;ing rate of burning which comprises so mix 7 ing soluble nitrocellulose with a relatively the 'colloided nitrocellulose which afterward completely tion of-tlie colloiding agent will take place substantially after distribution of the flame propagating cellulose. completely colloiding and forming into grains, whereby the colloided cellulose grains will be intercellularly impenetratedi with the flame propagating agentand the rapid combustion of the latter will carry the flame rapidly from the exposed surfaces into the interior of the grains and effect a relatively early complete consumption of the powder.

7. The process of making fiashless explosive powder which comprises so mixing soluble n trocellulose with black powder and. 'a nitrocellulose colloiding agent that the ac agent throughout the nitrotion of the cclloiding agent will take place p substantially after distribution of the black what we claim anddesire to protect by Let grains, whereby the colloided cellulose grains will be mtercellularly impenetrated with the black powder and the rapid combustion of the latter will carry theflame rapidly from the exposed surfaces into the interior of the grains and effect a relatively early complete consumption of the powder.

8. The process of making fiashless smoke less propellantpowder with a progressively increasing rate of boring which comprises adding to and thoroughly incorporating with soluble nitrocelluloseo flame propagating agent, together with ether and alcohol, completely colloiding and retaining the flame propagating agent in the colloided finished explosive.

9. The process of making fiashless smoke less propellant powder with aprogressively increasing rate of burning which compmses adding to and thoroughly incorporating with soluble nitrocellulose between from one-halfto one per cent to twenty er cent of a flame propagating agent together with ether and alcohol and completely colloiding to producea powder containing such agent in distributed forn'u I I 10. The process of making flashless smokeless propellant powder which comprises addin to and thoroughly incorporating with so uble nitrocellulose a relatively small proportion of black powder together'with' ether and alcohol.

11. The recess" of making flashlesssmokeless prope lant powder with a progressively increasing rate of burning which comprises adding to nitrocellulose a small proportion of an agent adapted to give a relatively ,quick local combustion, and intimately incorporatingv said nitrocellulose with, said agent andcompletely colloidiiig the 'nitrocellulose by a suitable solventi .,I

12. The process of making flashless smokeless propellant powder which comprises adding to soluble nitrocellulose a small proportion of black powder, and intimately incorporating said nitrocellulose and said black powder together with a suitable solvent.

13. A flashless smokeless propellant powder with a progressively increasing rate of burning. which comprises at least eightyper cent of completely colloided nitrocellulose containing approximately one-half of one per cent to twenty per cent of a flame propagating agent thoroughly distributed throughout the mass of the nitrocellulose.

14. A flashless smokeless propellant powder which comprises at least eighty per cent of colloided nitrocellulose containing a relatively small proportion of black powder distributed throughout the mass of the nitrocellulose.

15. A propellant explosive -containing loided nitrocellulose carrying a flame propagating agent within its cells.

18. A perforated smokeless and flashless powder consisting of cellular integral bodies of colloided nitrocellulose carrying a flame propagating agent within its cells.

19. As a new type offlashless smokeless propellant powder, perforated bodies of relatively slow burning colloided nitrocellulose, said bodies being cellular and' containing solids within the cells adapted for quick disappearance during combustion with production of open cavities. I

20. As a new flashless smokeless propellant, a perforated owder grain of colloided nitrocellulose, saic grain being of honeycomb structure and containing a flame propagating solid within the cells of the honeycomb.

21. As a new flashless smokeless propellant, a perforated powder grain of colloided nitrocellulose, said grain being of honeycomb structure and containing black powder within the cells of the honeycomb.

In testimony of which invention, we have hereunto set our hands, at Wilmington, Delaware, on this 22nd day of April, 1920.

FRANCIS I. DU PoNT. ERNEST DU FONT. 

